HVAC - Air Side: Terminal Units

SKU: RVI-11461Duration: 20 Minutes

The purpose of Heating, Ventilation and Air Conditioning systems (commonly referred to as HVAC systems) is to provide environments that are comfortable for people and that allow equipment to operate safely and reliably. Residential, commercial, and industrial facilities use HVAC systems. An HVAC system is a group of components working together to "condition" the air in an enclosed space. The components ensure that the air in this space is clean and odor free, and that its temperature, humidity, and the circulation rate is within desired ranges. This interactive online course focuses primarily on the terminal units, or VAVs, that increase the efficiency and add flexibility to an HVAC system.

Course Details


Training Time: 20 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English

Learning Objectives

  • Explain the principle behind Variable Air Volume (VAV) systems
  • Identify the different types of VAV terminal units
  • Describe how to control VAV terminal units
  • Determine how to maintain, troubleshoot and repair terminal units

Key Questions

The following key questions are answered in this module:

What is the purpose of HVAC systems?
The purpose of HVAC systems is to provide environments that are comfortable for people and that allow equipment to operate safely and reliably.

What are terminal units?
Terminal units are boxes that are located within the air duct system near to where the conditioned air discharges into a space.

What is fan powered VAV units (FPUs)?
Fan powered units (FPUs) are terminal units with fans.

What are the two types of FPUs?
The two types of FPUs are series-flow and parallel-flow boxes.

When are fan powered units typically used?
Fan powered units are typically used in building perimeter zones and other locations where the thermal loads are more variable.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

There two types of FPUs, series-flow and parallel-flow boxes. Each type has somewhat different characteristics. In a series FPU, the fan is in series with the primary airflow, but the suction of the fan is also open to the return air plenum. The fan operates continuously. In maximum cooling mode, the primary air damper is entirely open, and the pressure in the primary duct means that most of the air passing through the fan is cool supply air. As the need for cooling drops off, the damper closes, but the volume of discharge air remains constant as the fan starts to pull in warmer air from the return opening. This action causes the discharge temperature to increase. Some series FPUs have provisions for changing the fan speed. Fan speed affects the balance of plenum to primary air, which affects outlet air temperature. A misadjusted, above-normal fan speed will pull in excessive warm plenum air, creating a high discharge air temperature that may become the source of a hot call. Fan speed also affects the overall system air balance. The fan speed should only be set during air balancing; it should not be used as a method to change the local temperature.
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